Processes for obtaining substantially pure 4,4&#39; - dihydroxy - diphenyl-propane-2,2



' THREE COMPONENT PHASE Oct. 20, 1970 I ENYL-PROPA 2,2

Filed Ma 4, 1963 J. DE JONG PR SSES FOR OBTAINING SUBSTANTIALLY PURE-DIHYDROXYDI I\E SYSTEM AT 80C. .2m u

"QVAYVA INVENTOR. JAN IDE DE JONG ATTORNEY United States Patent Claimspriority, application Netherlands, Feb. 12, 1960,

Int. Cl. C07c 37/22 US. Cl. 260-619 7 Claims ABSTRACT OF THE DISCLOSURESubstantially pure diphenylol-propane is obtained, from the acidcontaining condensation reaction product of phenol with acetone in thepresence of an acid catalyst, by heating a mixture of such reactionproduct with water and a water immiscible organic solvent selected fromtoluene, xylene, monochlorobenzene, 1,1,2,2-tetrachloroethane andl,2-dichloroethane, with the amount of water being between 10% and1000%, by weight, and the amount of the solvent being between 10% and400%, by weight, each based on the amount of diphenyl-propane, and withthe temperature to which the mixture is heated being below the boilingpoint thereof and in the range between 70 C. and 100 C., at whichtemperature there is formed a wholly liquid system including an organicphase containing the solvent, at least 20% of diphenylol-propane and aminor part of water, and an aqueous, acid containing phase.

This invention relates generally to the production of4,4-dihydroxy-diphenyl-propane-2,2, hereinafter referred to asdiphenylol-propane or D.P.P., and more particularly is directed toimproved processes for obtaining substantiallypure diphenylol-propane.The present application is a continuation-in-part of my copendingapplication for US. Letters Patent Ser. No. 85,754, filed Ian. 30, 1961and now abandoned.

It is well known that diphenylol-propane may be obtained by thecondensation of phenol with acetone in the presence of acidic condensingagents. The process has been the subject of many experimentalinvestigations designed to improve the yield and the purity of thediphenylol-propane thus obtained. For example, it has been found thatthe strength of the acid solution is of importance, sulphuric acid ofabout 70% having been used for this purpose, and that the viscosity ofthe reaction mixture may be reduced by employing excess amounts ofeither phenol or sulfuric acid.

In all these modifications, the diphenylol-propane is obtained as veryfine crystals, which causes difficulty in effecting the separation ofthe solid product from the mother liquid by either filtering orcentrifuging.

It has also been proposed to carry out the manufacture ofdiphenylol-propane in the presence of inert liquid diluents, forexample, liquid hydrocarbons, as in British Pat. 428,944, correspondingto US. Pat. No. 1,978,949, or halogenated hydrocarbons, as in BritishPat. 557,976, which diluents do not participate in the reaction, but arecapable of preventing, or at least lessening, side reactions and, at thesame time, ensure that the end product will be in a form that can becentrifuged or filtered.

The product obtained by these methods employing diluents has eithertoluene present in an amount of about 3 to 5 or carbon tetrachloridepresent in an amount of about 5%, calculated on the amount of phenolused, and has an average melting point of 153 to 157 C. and a purity of98%. Its color, expressed as the extinction (X 100) of its 5% alcoholicsolution at 430 mu, is about 10 to 20, if for each batch fresh sulphuricacid has been used, and about 30 to 40, if the acid is used for a secondtime.

Although centrifuging is less difficult than if no organic diluent isused, this step of the process is still a source of difficulty. Aftercentrifuging, the product must be washed with water, neutralized andpurified by steaming. Further, in order to reduce the costs involved,the acid must be recovered and recirculated or reused after beingbrought up to strength by adding strong acid thereto. If fresh acid isused for each batch, the amount of acid required for each batch is aboutfour times the amount of diphenylol-propane that is obtained. In casethe acid is reused, the amount of new acid used for each batch can bereduced to about one-quarter, so that the ratio of diphenylol-propaneobtained to sulphuric acid used becomes about one to one.

It is also known that substantially pure diphenylolpropane may beobtained by heating the crude condensation product, which may stillcontain acid With water, in the presence of a base (pH7-9).

However, the product thus purified still contains those impurities whichare not easily soluble in water, such as isomers of D.P.P. and lowercondensates of phenol and acetone (the so-called resin). Theseimpurities which are not very soluble in water may be removed byrecrystallizing the D.P.P. out of an organic solvent, for example,toluene or xylene. Such a procedure for removing the water insolubleimpurities has its disadvantages as relati vely large quantities ofsolvent are required (for in stance 3 to 10 times the quantity ofD.P.P.), and the starting product must be acid-free, as otherwise theD.P.P. might decompose during recrystallization.

Accordingly, it is an object of the present invention to provideprocesses for obtaining pure diphenylol-propane, and which avoid theabove mentioned disadvantages of the processes previously proposed forthat purpose.

In accordance with an aspect of this invention, diphenylol-propane ofgreatly improved color and purity is obtained from the condensation ofphenol with acetone in the presence of a strong acid and promoter byadding suitable amounts of additional water and a water immiscibleorganic solvent or diluent preferably selected from the group consistingof toluene, xylene, monochlorobenzene, l,1,2,2-tetrachloroethane and1,2-dichloroethane; heating the mixture to a temperature which is belowthe boiling point thereof and at which temperature there forms a whollyliquid system having present therein at least an organic phasecontaining at least 20%, by weight, of diphenylol-propane, organicsolvent and minor parts of water; cooling the system below thecrystallization point thereof so that pure diphenylol-propanecrystallizes from that organic phase; and separating the purecrystalline diphenylol-propane from the liquid.

It has been found that pure diphenylol-propane may be obtained inaccordance with the invention, as described above, by adding theselected organic solvent to the condensation reactants, so that thecondensation reaction of phenol with acetone occurs in the presence ofthe organic solvent and thereafter adding the water, or by adding theorganic solvent and additional water to the acid-containing condensationreaction product or crude diphenylolpropane.

In order to obtain the desired pure diphenylol-propane, the selectedorganic solvent or diluent is added in an amount between 10% and 400%,by weight, of the amount of diphenylol-propane in the condensationreaction product or to be obtained from the condensation 3 reaction,while the water is added in an amount between and 1000%, by weight, ofsaid amount of diphenylol-propane. Further, in order to obtain thewholly liquid system, the mixture is heated to a temperature between 70and 100 C.

The advantages of the processes embodying this invention over thosepreviously proposed, as in the above identified patents, are as follows:

Fresh acid is always used, but the amount of acid required is not morethan the amount of diphenylolpropane obtained;

No difficulties whatever are encountered in effecting the isolation ofthe diphenylol-propane by centrifugation or filtration, if necessary ordesired.

The product obtained is practically colorless, in that it has a color of2 to 10, calculated as above, instead of 10 to or to 40, as in theproducts previously obtained;

The diphenylol-propane obtained has a solidification point of 156 C.,instead of a melting point of 153 to 157 C.; and

The purity of the obtained diphenylol-propane is about 99.9% instead of98%.

The diluents which are suitable for use in the process according to theinvention have the following general characteristics:

Immiscible, or at the most only poorly soluble in water, even attemperatures in the region of to 100 C.;

The solubility of diphenylol-propane in the diluent or solventpreferably should be poor, in order that only a small quantity ofdiphenylol-propane is taken up in the organic solvent, while the organicimpurities of the diphenylol-propane, such as, the isomericdiphenylol-propane compounds, the formed resin and also unreactedphenol, must be substantially soluble in the diluent; and

The diluent should provide a mixture with diphenylolpropane and waterthat is fully liquid upon heating to a temperature that lies beneath theboiling point of the azeotrope. Thus, generally, the boiling point ofthe azeotrope of water and organic solvent must lie betweenapproximately 70 C. and 100 C. (at atmospheric pressure).

Although specific solvents have been mentioned above as being usable inthe processes embodying the invention, it is to be noted that otherorganic solvents or diluents can be used provided that they have theabove noted necessary characteristics.

Prior to the crystallization of the diphenylol-propane from the organicfraction of the wholly liquid system, the liquid phases of the latterare separated and the acidic aqueous phase is discarded, whereupon theorganic fraction is neutralized to a pH of about 4.0 by adding freshWater or a basic solution before cooling to effect crystallization.After distillation of the mother lye, the organic solvent can be reused.This mother lye, from which the pure diphenylol-propane has beencrystallized, contains the impurities and unreacted phenol which can beseparated by distilling off the solvent, whereas the acidic aqueousphase can be reused for the melting of the next batch.

As shown on the accompanying drawing, which represents the three phasediagram of diphenylol propane, toluene and water at 80 C., the systemformed by the selected organic solvent or diluent, water and the crudediphenylol-propane at a temperature slightly below the boiling point ofthe mixture, may have a phase L which consists mainly ofdiphenylol-propane and the organic solvent, an aqueous acidic phase Land also an organic phase L containing little diphenylol-propane. In thecase of such a three phase system, the crystallization point below whichthe organic phase rich in diphenylol-propane is cooled to causecrystallizing of the latter is the ternary transition point of thatorganic phase. However, the wholly liquid system may contain only asingle organic phase, that is, be only a two phase system, in which casecrystallization of the diphenylol-propane is obtained by cooling theorganic phase below the crystallization point thereof.

The processes embodying the invention may be performed continuously orbe of the batch type, and are illustrated by the following specificexamples:

EXAMPLE I 200g. of crude D.P.P., containing 0.06 percent H SO wereheated in a round bottom flask together with 600 g. of water, 3 g. ofNaCl and 200 ml. toluene until the D.P.P. wholly liquified (at atemperature below about C.). Thereupon the mixture was cooled down to 60C. with stirring in about 15 minutes. Then the stirring was stopped, andthe upper or toluene containing layer was separated (198 ml.) with about400 ml. of water. After adding 400 ml. fresh water, the D.P.P. wassteamed until all toluene had been removed (8 ml. were caught). TheD.P.P. melt thereafter was poured out. After drying, this product had amelting point of 156.7-159.3 C. and a contents of p.p.' isomer of 99.9%;the solidification point was 156.6 C.

Thecrude product had a p.p.' content of 97%, and a melting point of137156 C. After cooling to effect the isolation of the D.P.P. thatsolidified in crystalline form from the separated toluene layer and theseparated water layer, the efiieiency of the purification processamounted to 96.5%, that is to say, about 99.5% cal-. culated on purep.p.' isomer. The loss of toluene amounted to 3 ml.

EXAMPLE II The toluene of Example I was replaced by the same amount oftechnical xylene. The purification was effected in a manner analogous tothat described in Example I, and pure D.P.P. was obtained with a meltingpoint of 155.9159.l C.

EXAMPLEIII The method described in Example I was followed until' thetoluene layer had separated. Then the crystalline solidified D.P.P. wasremelted with 400 ml. of fresh water, 2 g. of NaCl and 200 ml. freshtoluene. After cooling down to 55 C., the toluene layer was removed, andthe crystal mass was freed of residual toluene by steaming, after whichthe liquid D.P.P. was cooled while being stirred. The product obtainedhad a melting point of 157.l159.4 C., and a p.p. content of 99.9%.

EXAMPLE V 200 g. of crude D.P.P. were melted with 600 ml. of water and 3ml. NaCl while being stirred, after which the emulsion was cooled downto 30 C. within 60 minutes time. Then the crystalline solidified productwas stirred with 200 ml. of benzene for 10 minutes. The benzene layerml.) was separated, and the residual benzene was removed by steamdistillation, after which the melted D.P.P. was cooled down to 60 C.while being stirred.'

The thus obtained clear and white coarse crystals had a melting point of155.8l58.7 C.

EXAMPLE VI 200 g. of crude D.P.P. were melted with 600 g. of water and200 ml. of tetra chloro-ethane, and then cooled down to roomtemperature, after which the crystalline solidified D.P.P. was separatedby centrifuging. The thus obtained product was washed in the centrifugewith water and thereafter was dried. The melting point was 156.8l58.9 C.

EXAMPLE VII 200 g. of crude D.P.P. were heated in 300 g. of water and 90ml. of toluene to 82 C., and then the mixture was cooled down to 20 C.and centrifuged. The D.P.P. had a p.p.' content of 99.8%, and a meltingpoint of 156.7-159 C.

EXAMPLE VIII 395 g. of phenol (4.2 moles) are dissolved in 736 g.toluene and, while stirring, 522 g. of 77.5 percent sulphuric acid and1.5 ml. thioglycolic acid are added at a temperature of 20 C. 116 g. (2moles) of acetone are slowly added to the mixture over a period of 3hours at 25 C. The mixture is stirred for another 7 hours at 35 C. tocomplete the condensation reaction of phenol with acetone in thepresence of toluene as the diluent in accordance with this invention.Thereafter, 1060 g. of Water are added and the whole is heated to atemperatureof 82 C. The aqueous acid layer is discarded and 1000 ml.fresh water are added. The pH of the aqueous layer is adjusted to 4 byadding sodium bicarbonate while intensely stirring. Then crystallizationis effected by cooling the mixture slowly down to 25 C. (within about 3hours), while stirring. The crystallized diphenylolpropane iscentrifuged and dried. The yield is 425 g. (93%), and has a meltingpoint of 156.4-158 C. The toluene layer mother lye from which thediphenylpropane was crystallized contained 14 g. of phenol and 17.4 g.of diphenylol-propane isomers. In the acid and water layers, 10.2 g. ofphenol and 7.6 g. of phenol sulfonic acid were still present.

EXAMPLE IX In a manner analogous to that described in Example VIII, 197g. of phenol (2.1 moles) are condensed with 58 g. of acetone (1 mole) inthe presence of 270 g. of 80 percent sulphuric acid, 1 ml. thioglycolicacid and 972 g. of monochlorobenzene as the diluent in accordance withthis invention. The acetone was added over a period of 1 hour at 25 C.,and thereafter stirring was continued, at a temperature of 35 C. for afurther 3.5 hours. The yield of pure diphenylol-propane was 205.2 g.(corresponding to about 90% of the theoretical value) and had a meltingpoint of 156.6 to l58.4 C.

EXAMPLE X The 972 g. of monochlorobenzene in Example IX were replaced by680 g. of 1,1,2,2-tetrachloroethane. In a similar mannerdiphenylol-propane was prepared. The dosing time of the acetone at 25 C.was again 1 hour, but thereafter the stirring was continued at 35 C. foronly 2.5 hours to complete the condensation reaction. The yield was187.5 g. of pure diphenylol-propane (about 82% of the theoreticalvalue), and had a melting point of 156.4 to 158 C.

Although specific examples of processes embodying the invention aregiven above, such examples are merely illustrative, and the invention isnot limited thereto except as defined in the appended claims.

What is claimed is:

1. In the process for producing diphenylol-propane by the condensationreaction of phenol 'with acetone in the presence of an acid catalyst,the steps for obtaining substantially pure diphenylol-propane comprisingheating a mixture consisting essentially of the acid containing reactionproduct, Water in an amount between 10% and 1000%, by weight, of theamount of diphenylol-propane in said reaction product, and a waterimmiscible organic solvent in an amount between 10% and 400%, by weight,of said amount of diphenylol-propane, said mixture being heated to atemperature between C. and C. which is below the boiling point thereof,and said organic solvent being selected from the group consisting oftoluene, xylene, monochlorobenzene, 1,1,2,2-tetrachloroethane and1,2-dichloroethane to form, with said diphenylol-propane and Water insaid relative amounts, a system which is wholly liquid at saidtemperature and which includes at least a first organic phase containingsaid solvent, at least 20% of diphenylol-propane and a minor part ofwater, and a second aqueous, acid-containing phase;

cooling below the crystallization point of said system,

thereby to cause substantially pure diphenylol-propane to crystallizetherefrom; and

collecting the crystallized pure diphenylol-propane.

2. The process as in claim 1:

wherein said aqueous phase is separated from said organic phase prior tothe cooling of the latter to efiect crystallization of thediphenylol-propane therefrom.

3. The process as in claim 2;

further comprising adjusting the pH value of said organic phase toapproximately 4.0 after separation of said aqueous phase therefrom.

4. The process as in claim 2;

further comprising distilling off the organic solvent from the remainderof said organic phase from which the diphenylol-propane is crystallized,and recovering the distilled organic solvent for reuse in subsequentpurifications of diphenylol-propane.

5. The process as in claim 1;

wherein said water of the mixture is in the form of a dilute aqueoussolution of sodium chloride.

6. The process as in claim 1;

wherein said mixture is formed by adding said water and said organicsolvent to said reaction product at the completion of the condensationreaction.

7. The process as in claim 1;

wherein said organic solvent is added to the condensation reactants sothat the condensation reaction occurs in the presence of said organicsolvent, and said water is added upon the completion of the condensationreaction.

References Cited UNITED STATES PATENTS 10/1934 Kohn et al. 11/1960Grimme et al.

FOREIGN PATENTS 12/1943 Great Britain.

OTHER REFERENCES LEON ZITVER, Primary Examiner N. P. MORGENSTERN,Assistant Examiner

